Macroevolution processes of Vertebrate and Mammalian Evolution - Class 4 - Chapter 5

4^th Class  – Chapter 5 – Macroevolution processes of Vertebrate and Mammalian Evolution.

I unfortunately missed this class because of the season’s allergies that were attacking me that week, but I did read the chapter and I will do an explanation based on the chapter.

It is important to understand that due to the large amount of living organisms, biology classifies categories based on their physical similarities. But biology also have to consider their evolutionary descendent. If a structure is shared by the same species taking in consideration they are descendants from a same ancestor, the structure is called homologies and that indicated an evolutionary relationship. If the similarities shared are from different ancestors the structure is called analogies and the processes that lead to the development of these analogies is called homoplasy.

To interpret evolutionary relationships, biologists use two schools. The first one being: Evolutionary systematics  that is the more traditional and Cladistics, they both share plenty of similarities, they both recognize that organisms should be compared using similar features, that some features are more informative than others, and they are both interested in tracing evolutionary relationships. But they do have some differences, for example the Cladistics is more explicit and rigorous when defining the kings of homologies that yield most useful information.

Despite of which approach, most biologist use biological species concepts to compare organisms. To understand what they are, it is important to understand first how they came about not forgetting  the fact that new species are usually created when present in an isolate condition.

Considering different types of variation of organisms, an organism that is multicellular and moves around is considered an animal. The vertebrates fall under the chordate phyla, which mean they are animals with a nerve cord.

The vertebrates receive this name because they have a vertebral column. They also have a developed brain and paired sensory structures. Vertebrates are divided into:

Cartilaginous fish

 Bony Fish

Amphibians

Reptiles­ 

Birds

Mammals

Personal Input

Missing this class was hard for me just because I feel like the book is very complicated at times, so I had to read several times the same parts to get an overall understanding of what the subject was.

It is really interesting to know biologists take the time to study the evolution of a certain organism that lived millions of years ago, just to be able to separate into groups current species.

I understand this subject was important to understand the classification of primates coming up in the next chapter.

Additional Information

For my additional information I decided to add some information on the differences between the Evolutionary systematics and the Cladistics:

This first link is a good explanation of the Cladistics. It gives an introduction, methodology, implications and what is the need for them:

http://www.ucmp.berkeley.edu/clad/clad1.html

This next link is in the same website, but it explains the evolutionary systematics, it presents graphics and presentations on the subject.

http://www.ucmp.berkeley.edu/education/events/carlson1.html